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Journal of mechanical science and technology 23건

  1. [국내논문]   Effects of fiber aspect ratio evaluated by elastic analysis in discontinuous composites   피인용횟수: 1

    Kim, Hong-Gun (Department of Mechanical and Automotive Engineering, Jeonju University)
    Journal of mechanical science and technology v.22 no.3 ,pp. 411 - 419 , 2008 , 1738-494x ,

    초록

    An elastic stress analysis to investigate the effects of fiber aspect ratio in short fiber reinforced discontinuous composite materials has been done for different fiber volume fractions. In order to examine the elastic internal behavior, an evaluation of the load bearing capacity of discontinuous reinforcements is needed in advance. Accordingly, analytical derivation of composite mechanics has been carried out to predict fiber stresses and fiber/matrix interfacial shear stresses in discontinuous composites. The model is based on the theoretical development of conventional shear lag theory developed by Cox. However, the major shortcoming of the Cox model is due to the calculation without normal stress transfer from the end of fibers. In order to overcome the shortcoming, both of the normal and shear stress transfer mechanisms between the fiber and the matrix are accounted for with the stress concentration effects as well as material and geometrical properties. Results of predicted stresses concerning the various fiber aspect ratios are described by using the present model that is the closed form solution and compared with the Cox model and Taya model. It is found that the effect of fiber aspect ratio is significant to composite strengthening through load transfer from the matrix to the fiber, whereas the effect of fiber volume fraction is not so sensitive, relatively. It is also found that the present model has the capability to correctly predict the values of fiber stresses and fiber/matrix interfacial shear stresses.

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  2. [국내논문]   Quantitative analysis of nonlinear joint motions for young males during walking  

    Park, Jung-Hong (Department of Mechanical Design Engineering Pusan National University ) , Son, Kwon (School of Mechanical Engineering Pusan National University ) , Kim, Kwang-Hoon (Department of Mechanical Design Engineering Pusan National University ) , Seo, Kuk-Woong (Department of Physical Education Pusan National University)
    Journal of mechanical science and technology v.22 no.3 ,pp. 420 - 428 , 2008 , 1738-494x ,

    초록

    Body motions associated with walking exhibit irregular and complex patterns with time. Chaos analysis methods have been developed to clarify nonlinearity of the lower extremity motions. No research has been reported on chaos analysis of the upper extremity joints. The purpose of this study was to investigate chaotic characteristics of movements of the upper body as well as the lower extremity during level walking. Gait experiments were carried out for eighteen young males. Each subject was instructed to walk on a treadmill at his own natural speed. Flexion-extension angles of eleven joints were obtained by using eight video cameras. To evaluate joint characteristics in a quantitative way, the largest Lyapunov exponent(LLE) was calculated from a reconstructed state space created by time series and embedding dimension. The mean LLE ranged from 0.080 to 0.137 for the upper body, and from 0.090 to 0.182 for the lower extremity joints. The mean LLE of the upper extremity joints was statistically different from that of the lower extremity joints(p

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  3. [국내논문]   Buckling analysis of multi-walled carbon nanotubes under combined loading considering the effect of small length scale   피인용횟수: 1

    Arani, A. Ghorbanpour (Department of Mechanical Engineering, Faculty of Engineering, University of Kashan ) , Rahmani, R. (Department of Mechanical Engineering, Faculty of Engineering, University of Kashan ) , Arefmanesh, A. (Department of Mechanical Engineering, Faculty of Engineering, University of Kashan ) , Golabi, S. (Department of Mechanical Engineering, Faculty of Engineering, University of Kashan)
    Journal of mechanical science and technology v.22 no.3 ,pp. 429 - 439 , 2008 , 1738-494x ,

    초록

    The torsional and axially compressed buckling of an individual embedded multi-walled carbon nanotube(MWNTs) subjected to an internal and/or external radial pressure was investigated in this study. The emphasis is placed on new physical phenomena which are due to both the small length scale and the surrounding elastic medium. Multiwall carbon nanotubes which are considered in this study are classified into three categories based on the radius to thickness ratio, namely, thin, thick, and almost solid. Explicit formulas are derived for the van der Waals(vdW) interaction between any two layers of an MWNT based on the continuum cylindrical shell model. In most of the previous studies, the vdW interaction between two adjacent layers was considered only and the vdW interaction among other layers was neglected. Moreover, in these works, the vdW interaction coefficient was treated as a constant that was independent of the radii of the tubes. However, in the present model the vdW interaction coefficients are considered to be dependent on the change of interlayer spacing and the radii of the tubes. The effect of the small length scale is also considered in the present formulation. The results show that there is a unique buckling mode(m,n) corresponding to the critical shear stress. This result is obviously different from what is expected for the pure axially compressed buckling of an individual multi-walled carbon nanotube.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  4. [국내논문]   An algebraic substructuring using multiple shifts for eigenvalue computations   피인용횟수: 2

    Ko, Jin-Hwan (Department of Aerospace Information Engineering, Konkuk University ) , Jung, Sung-Nam (Department of Aerospace Information Engineering, Konkuk University ) , Byun, Do-Young (Department of Aerospace Information Engineering, Konkuk University ) , Bai, Zhaojun (Department of Computer Science, University of California)
    Journal of mechanical science and technology v.22 no.3 ,pp. 440 - 449 , 2008 , 1738-494x ,

    초록

    Algebraic substructuring(AS) is a state-of-the-art method in eigenvalue computations, especially for large-sized problems, but originally it was designed to calculate only the smallest eigenvalues. Recently, an updated version of AS has been introduced to calculate the interior eigenvalues over a specified range by using a shift concept that is referred to as the shifted AS. In this work, we propose a combined method of both AS and the shifted AS by using multiple shifts for solving a considerable number of eigensolutions in a large-sized problem, which is an emerging computational issue of noise or vibration analysis in vehicle design. In addition, we investigated the accuracy of the shifted AS by presenting an error criterion. The proposed method has been applied to the FE model of an automobile body. The combined method yielded a higher efficiency without loss of accuracy in comparison to the original AS.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  5. [국내논문]   Elastic analysis of unbounded solids using volume integral equation method   피인용횟수: 1

    Lee, Jung-Ki (Department of Mechano-Informatics and Design Engineering, Hongik University)
    Journal of mechanical science and technology v.22 no.3 ,pp. 450 - 459 , 2008 , 1738-494x ,

    초록

    A volume integral equation method(VIEM) is used to calculate the plane elastostatic field in an unbounded isotropic elastic medium containing isotropic or anisotropic inclusions subject to remote loading. It should be noted that this newly developed numerical method does not require the Green's function for anisotropic inclusions to solve this class of problems, since only the Green's function for the unbounded isotropic matrix is involved in their formulation for the analysis. A detailed analysis of displacement and stress fields is carried out for isotropic or anisotropic inclusions. The method is shown to be very accurate and effective for investigating the local stresses in composites containing isotropic or anisotropic fibers.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  6. [국내논문]   Vibration characteristics of computer stacked disks and head assembly  

    Huang, Shyh-Chin (Department of Mechanical Engineering, National Taiwan University of Science and Technology ) , Lin, Kao-An (Department of Mechanical Engineering, National Taiwan University of Science and Technology)
    Journal of mechanical science and technology v.22 no.3 ,pp. 460 - 468 , 2008 , 1738-494x ,

    초록

    A stacked multi-disk with read/write head assembly was investigated. The interference of head assembly on the spinning disks was modeled by stationary springs intervening between disks. The receptance method was then applied to join the spinning disks and the stationary springs. A general, recursive equation for natural frequency of a disk-head system was derived. Numerical examples followed for the cases of 3 to 6 stacked disks. The results showed that even for weak spring coupling, the changes of mode shapes were very significant and the changes of natural frequencies were slight. The effects of spring stiffness, location, and disk spinning speed were examined as well. The spinning speed was seen to pull the frequency loci to pass through the crossings of a single disk's frequency curves and there existed a curve-veering phenomenon.

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  7. [국내논문]   Safe physical human robot interaction-past, present and future   피인용횟수: 1

    Pervez, Aslam (Human-Machine-Computer Interface Lab, Department of Mechatronics, School of Information and Mechatronics, Gwangju Institute of Science and Technology(GIST) ) , Ryu, Je-Ha (Human-Machine-Computer Interface Lab, Department of Mechatronics, School of Information and Mechatronics, Gwangju Institute of Science and Technology(GIST))
    Journal of mechanical science and technology v.22 no.3 ,pp. 469 - 483 , 2008 , 1738-494x ,

    초록

    When a robot physically interacts with a human user, the requirements should be drastically changed, The most important requirement is the safety of the human user in the sense that robot should not harm the human in any situation. During the last few years, research has been focused on various aspects of safe physical human robot interaction. This paper provides a review of the work on safe physical interaction of robotic systems sharing their workspace with human users(especially elderly people). Three distinct areas of research are identified: interaction safety assessment, interaction safety through design, and interaction safety through planning and control. The paper then highlights the current challenges and available technologies and points out future research directions for realization of a safe and dependable robotic system for human users.

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    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  8. [국내논문]   Fatigue life prediction of a cable harness in an industrial robot using dynamic simulation   피인용횟수: 2

    Yoon, Ji-Won (Graduate School of Mechanical Engineering, Ajou University ) , Park, Tae-Won (Department of Mechanical Engineering, Ajou University ) , Yim, Hong-Jae (Department of Mechanical Engineering, Kookmin University)
    Journal of mechanical science and technology v.22 no.3 ,pp. 484 - 489 , 2008 , 1738-494x ,

    초록

    The cable which transfers the signal and power in an industrial robot has a problem of fatigue fracture like steel components. Since the cable is very flexible compared to other components of the system, it is difficult to estimate its motion numerically. Some studies have been done on a large deformation problem, especially in a cable, and a few attempts have been made to apply the absolute nodal coordinate formulation(ANCF), which can simulate a large deformation. Only researches about the fatigue life of structural cables or comparative studies of FEM and ANCF simulations can be found. This paper presents a method to simulate the behavior of the cable harness using the ANCF and to predict the fatigue life while computing the strain time history of the point of interest. Rigid body dynamics is applied for the robot system, while ANCF is used for the cable harness. The simulation is performed by using the dynamic analysis process. The material property of the cable is obtained by a test. A simplified model is prepared. With these data, the behavior of the cable is simulated and the fatigue life is predicted.

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  9. [국내논문]   Optimal feature selection using genetic algorithm for mechanical fault detection of induction motor  

    Nguyen, Ngoc-Tu (School of Electrical Engineering, Ulsan Univ. ) , Lee, Hong-Hee (School of Electrical Engineering, Ulsan Univ. ) , Kwon, Jeong-Min (School of Electrical Engineering, Ulsan Univ.)
    Journal of mechanical science and technology v.22 no.3 ,pp. 490 - 496 , 2008 , 1738-494x ,

    초록

    Time-domain vibration signals are measured in all horizontal, axial, and vertical directions for induction motor mechanical fault diagnostics. Many features are extracted from these signals. The problem is how to find the good features among the feature set in order to receive reliable classifications. Based on specific distance criteria, a genetic algorithm(GA) is introduced to reduce the number of features by selecting optimized ones for fault classification purpose. A decision tree and multi-class support vector machine are used to illustrate the potentiality and efficiency of this selection method. Comparisons show that the diagnostic systems after selecting specific features perform better than the original system.

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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  10. [국내논문]   Fuzzy MRAC controller design for vane-type air motor systems   피인용횟수: 3

    Hwang, Yean-Ren (Department of Mechanical Engineering and the Institute of Opto-Mechatronics Engineering, National Central University ) , Shen, Yu-Da (Department of Mechanical Engineering, National Central University ) , Jen, Kuo-Kuang (Department of Mechanical Engineering, National Central University)
    Journal of mechanical science and technology v.22 no.3 ,pp. 497 - 505 , 2008 , 1738-494x ,

    초록

    Air motors are widely used in the automation industry due to special requirements, such as spark-prohibited environments, the mining industry, chemical manufacturing plants, and so on. The purpose of this paper is to analyze the behavior of a vane-type air motor and to design a model reference adaptive control(MRAC) with a fuzzy friction compensation controller. It has been noted that the rotational speed of the air motor is closely related to the compressed air's pressure and flow rate, and due to the compressibility of air and the friction in the mechanism, the overall system is actually nonlinear with dead-zone behavior. The performance of the previous controllers implemented on an air motor system demonstrated a large overshoot, slow response and significant fluctuation errors around the setting points. It is important to eliminate the dead-zone to improve the control performance. By considering the effects of the dead-zone behavior, we have developed an MRAC with fuzzy friction compensation controller to overcome the effect of the dead-zone. The following experimental results are given to validate the proposed speed control strategy.

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    회원님의 원문열람 권한에 따라 열람이 불가능 할 수 있으며 권한이 없는 경우 해당 사이트의 정책에 따라 회원가입 및 유료구매가 필요할 수 있습니다.이동하는 사이트에서의 모든 정보이용은 NDSL과 무관합니다.

    NDSL에서는 해당 원문을 복사서비스하고 있습니다. 아래의 원문복사신청 또는 장바구니담기를 통하여 원문복사서비스 이용이 가능합니다.

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